Effect of Salinity Stress on Ribonucleolytic Activities in Glycophytic and Halophytic Plant Species

Abstract

Summary The ribonuclease activities (RNase, EC 2.7.7.17) of the halophyte, Suaeda maritima (L.) DUM var. macrocarpa MOQ, and the glycophytes, Phaseolus vulgaris (L.) and Vicia faba (L.), were studied in relation to the salinity (NaCl) of the nutrient medium. A reduction of growth was observed for the three species subjected to «salt stresso (i.e. hypersalinity for glycophytes or absence of salt for the halophyte). Both short-term (salt shock) and long-term treatments with NaCl induced a marked increase in RNase activity, and a close relationship was established between «salt stress» and a high RNase activity. The stimulation of RNase activity was independent of the species (halophyte or glycophyte), the analyzed organ (root or leaf) and the nature of the salt treatment (saline shock or steady state culture). Ribonuclease activities of S. maritima leaves and V. faba roots were studied in detail by ion-exchange chromatography. Under the influence of salt treatment it appears that both anionic and cationic RNase activities were increased. It has been demonstrated for the first time that an anionic RNase is stimulated to a greater extent than any other ribonucleolytic enzyme in both the halophyte and the glycophyte. The RNases, particularly the anionic enzymes, can thus be considered as good markers for conditions of saline contraint.